The invention relates to the field of imaging systems, and particularly relates to imaging systems in which a continuous web of media is fed through an imaging apparatus.
Imaging systems that feed recording media through an imaging apparatus may include a movable optical carriage that displaces a beam of light from an imaging source, such as a laser. The carriage moves in a direction transverse to the direction of movement of the web in a slow scan to expose a supply of recording media to the light beam. Such a carriage for use in an imaging system including an internal imaging drum for supporting the recording media, is disclosed for example in U.S. Pat. No. 5,598,739, the disclosure of which is hereby incorporated by reference.
As shown in FIG. 1, in a conventional imaging system 10 including an imaging drum 12, a web of image recording media 14 travels from a supply cassette 16 around the inner support surface 18 of the drum 12 to a take up cassette 20. The media generally has sufficient inherent stiffness that it maintains the cylindrical shape of the inner surface 18 of the drum 12 when coupled to cassettes 16 and 20. A movable carriage 22 may be used to position a beam of laser light 24 on desired portions of the recording surface 26 of the media 14. The imaging system 10 is typically coupled to a computer controlled image processor (not shown). The media is typically driven through the system by drive rollers 28 and 30.
Each cassette 16 and 20 is typically sealed from light as appropriate, and each provides an elongated opening through which the web of media may pass as it exits the supply cassette 16 and enters the take up cassette 20. The cassettes may be loaded into the system via access openings and/or by removing a top cover. A portion of the media extending from supply cassette must be fed between the drive rollers 28 so that it may be drawn from the supply cassette and fed through the imaging system. One of the rollers 28 may be separable from the other roller to facilitate the introduction of the media therebetween. This leading portion is necessarily exposed to light during conventional operation of the imaging system.
It is desirable that the media be fed between the drive rollers in optimal alignment with the imaging region. If the leading portion of the media is shifted to one side or the other as it enters the nip between the rollers 28 (or as the rollers 28 come together to sandwich the media), then the media will not be aligned. Also, if one side edge of the media is fed in advance of the opposing other side edge, then the media will not be aligned with the imaging region. Precise alignment of the photosensitive media is critical, as entire multicolor printing operations of very high resolution depend on the proper orientation of the imageable media within the imaging region. Potential problems exist where the media must be fed by hand between the drive rollers, particularly when the leading edge of the web of media is not cut squarely, and/or when buckles are formed in the media between the supply cassette and the drive rollers.
It is desirable to provide a media supply system that is accurate and relatively easy to use, yet involves relative little mechanical complexity. It is further desirable to provide a media supply system that is relatively economical to produce.